HIV surveillance using unlinked anonymous HIV testing of discarded blood samples has yielded important information; most such efforts rely on selected patient populations. Unlinked anonymous HIV testing of semen in discarded condoms may be a way to assess HIV in an unselected sample of men in public sex environments or who are clients of sex workers. Testing the semen of men who use condoms in these two contexts is important because in high risk environments such as public sex environments (PSEs) or environments where drugs are used men may use condoms inconsistently. Previous research indicates that men who are clients of female sex workers (FSWs) or who use PSEs may use condoms in those contexts but not with their regular partners and this research can provide an indirect assessment of potential risks to other groups. The goal of this feasibility study is to test components of a method for assessing HIV, illegal or prescribed drugs, sexually transmitted disease, or other infectious disease in two hidden populations; men who 1) frequent PSEs or 2) are clients of FSWs. Specifically, we are developing and testing methods to test semen captured in discarded condoms found in PSEs and assessing the feasibility of asking FSWs to collect used condoms following sexual encounters with their male clients. These methods may result in relatively low-cost methods for surveillance of high-risk groups and may have international applications but multiple concerns with respect to testing protocols and condom collection methods support the need for careful development of methods before incorporation into a larger project. The specific aims of this project are: 1) To test the reliability of semen and HIV antibodies in discarded or collected condoms in the laboratory and assess fitness of collected specimens for HIV testing after exposure to variations in time and temperature. 2) To map the discard rate, locations and condition of discarded condoms in a PSE in Boston. 3) To discover, through the use of ethnographic interviewing, the normative practices in condom use and disposal of FSWs and men who attend PSEs. 4) To conduct focus groups with FSWs to determine their perceptions of the feasibility of condom collection from their clients. 5) To conduct an ethical review of the issues underscoring unlinked anonymous HIV testing of discarded and collected condoms and other human subjects concerns raised by this study design.